1. Field of the Invention
The present invention relates to a power semiconductor module in which partial discharge is reduced to achieve a longer operating life.
2. Background Art
A conventional power semiconductor module, such as that proposed in Japanese Laid-Open Patent Publication No. 2002-76197, includes: a heat sink; a circuit substrate(s) mounted on the heat sink; a conductive pattern provided on the circuit substrate; a case provided on the heat sink so as to enclose the circuit substrate; a soft insulator filling the space within the case; and a solid insulator provided on the top surface of the circuit substrate such that it is in contact with the peripheral portion of the conductive pattern. The solid insulator is intended to enhance the insulation resistance and the withstand voltage of the module.
However, when the power semiconductor module is used at a high voltage, a partial discharge may occur from a floating potential portion within the module, resulting in insulation failure. It has been found that drive circuit substrates having electrodes on both sides and having a complicated shape are especially susceptible to partial discharge.